As a method of generating three-dimensional ultrasonic image data (i.e., ultrasonic volume data, hereinafter, referred to as volume data) by using an ultrasonic diagnostic apparatus, there is a known method of generating volume data by arranging a series of ultrasonic tomographic images which are acquired by imaging an object at a predetermined frame rate while an ultrasonic probe is being moved. In this method, it is important for acquiring volume data having sufficiently uniform data density that an ultrasonic probe is moved at a constant velocity. When an ultrasonic probe is moved at a constant velocity and imaging is performed at a predetermined frame rate, it is possible to acquire isochronal ultrasonic tomographic images and volume data with uniform data density.
For instance, in the case of generating respective images of arbitrary cross-sections from volume data, image quality of these cross-sectional images depends on data density of the corresponding cross-sections in the volume data. Data density of volume data depends on velocity of an ultrasonic probe. Thus, for instance, when a velocity component of an ultrasonic probe in the direction along the target cross-section to be extracted in the form of an image increases, data density within this target cross-section is reduced and image quality of this target cross-section is deteriorated. Hence, in order to acquire a cross-sectional image with satisfactory image quality from volume data, it is desirable to move an ultrasonic probe at a speed within a predetermined speed range.